The ABC of vitamins and supplements

They’re vital to our health and wellbeing and you may feel you already know a bit about vitamins. But do you really understand how they can help you fight cancer? here’s my ABC of what you need to know:

VITAMIN A

WHAT: Vitamin A is a fat-soluble pigment found in fish and dairy food.

Vitamin A can also be made by the body using the carotenoid group of polyphenols (found in orange fruit and vegetables from carrots to pumpkins and apricots).

WHY: Important for forming healthy cells in our skin, the cornea of the eye, and the membranes of your mouth.

Vitamin A is a powerful antioxidant which acts directly on free radicals.

Although diets high in vitamin A are healthy and linked to a lower risk of many diseases, the same cannot be said of supplements, because they offer concentrated doses of vitamin A. This, as I explained earlier on, can upset the ‘oxidative’ balance by destroying too many free radicals (and as we’ve seen your body needs some in order to function properly).

Two large studies giving extra vitamin A to smokers had to be stopped because of an increased lung cancer rate. Another large human dietary prevention study found that men who started the trial with low blood levels of vitamin A had lower levels of prostate cancer after years of taking a vitamin A supplement.

However, men who had high initial levels of vitamin A ended up with a higher risk of prostate cancer.

The clear take-home message here is this: correcting a natural or acquired deficit is beneficial but, too much of a good thing, in this case a single antioxidant, can be harmful. FOUND IN: Oily fish, cod liver oil, other fish oils; beef, pork, lamb, chicken liver and kidney; eggs, milk, cream, yoghurt and cheese.

VITAMIN B

WHAT: There are several subtypes of these water-soluble vitamins: B1 (thiamine), B2 (riboflavin), vitamin B6 (pyridoxine), B9 (folic acid) and B12 (cobalamin).

WHY: This group helps the body turn food into energy and is also key for brain development and producing red blood cells.

B vitamins have a complex relationship with cancer risk. Studies show women with a diet high in B vitamins have a lower risk of breast cancer — and also that people deficient in B vitamins had an increased risk of cancer, especially of the bowel.

A combined analysis of two studies from Norway investigating whether giving people vitamin B supplements after a heart attack would aid recovery actually reported a slightly higher incidence of subsequent cancers. FOUND IN: Grains such as wheat, barley, and oats (B1 and B2), leafy green vegetables (B6 and B9), plus beetroot, chickpeas, salmon, tuna and citrus fruits, meat and some legumes (B12).

VITAMIN C

WHAT: Vitamin C is an essential water-soluble nutrient which humans need to eat on a daily basis. The body cannot manufacture its own supplies and it only lasts for a short period in the bloodstream.

It plays an important role in the functioning of several enzymes, healing wounds, and repairing and maintaining bones and teeth. It also helps the body absorb iron from non-meat sources such as vegetables and nuts. It’s often described as an antioxidant, but this is not actually correct, as it cannot act directly to neutralise free radicals in the same way that vitamins E and vitamin A can — even at high doses. But it is involved in a mechanism which enables DNA to ‘sense’ the oxidative damage being done by free radicals, viral and bacterial infection — so, in this respect, it is a vital part of DNA repair to prevent potential cancerforming mutations. There’s evidence vitamin C may also have cancerprotective properties by limiting the formation of carcinogens — these include some of the toxins produced when your body digests meat for instance. Research also shows that higher consumption of fruits and vegetables is associated with lower risk of most types of chronic disease, including cancer. This may be in part due to their high vitamin C content.

Several studies show that chronic deficiency can increase the risk of cancer.

A recent review reported that women who either took vitamin C supplements or increased their dietary intake of vitamin C after being diagnosed with breast cancer significantly reduced their risk of dying from it.

However, research shows that while being deficient in vitamin C increased the risk of cancer — eating more than the recommended amount had no effect.

And although there is currently a trend for intravenous vitamin C infusions as an alternative therapy or health kick, there are no robust trials or credible data to back up its use — other than perhaps for someone with a genuine vitamin C deficiency.

Unlike vitamins A and E, however, there’s no data to show

that vitamin If considering taking C can high cause a supplement, amounts of cancer. recommend you take no more than 100mg a day. FOUND IN: Citrus fruits, cherries guavas, yellow peppers. blackcurrants and blackberries are particularly rich in vitamin C

VITAMIN D

WHAT: important amount in the to muscles keep body of Vitamin WHY: calcium role shown — bones, healthy. nutrients in Research and regulating D that teeth phosphate plays vitamin neede and has the and D protect against kidney, can bowel the help risk of you and to direct ies prostate Numerous show abilities it cancer. also study have that delay its slow spread. cancer growth and regular Survivors exposure of bowel to cancer sunlight with and higher vitamin D level were of relapsing. found to have a lower risks But most fascinating of all, as explained in Saturday’s paper is a study that focused on people who’d been treated for melanoma skin cancer. As the disease increases with sunburn these patients had been torn, to avoid direct sunlight after their diagnosis. However, those who ignored the advice and continued to have

regular sun exposure were subsequently found to actually have a lower risk of the melanoma spreading due to a deficiency of vitamin D.

And there’s evidence that being overweight (itself a cancer risk) can lead to vitamin D deficiency — an extra reason why losing a spare tyre can cut your cancer risk.

The authors of the Genetic Investigation Of Anthropometric Traits (Giant) study, which followed 120,000 people, concluded that because vitamin D was stored in fatty tissue, obese people therefore had less circulating in their blood and available to combat arthritis, osteoporosis, infertility, and dementia — as well as cancer.

FOUND IN: Your body needs exposure to sunlight to create about 80 per cent of the vitamin D it needs — with the result that many people are vitamin D deficient during the winter months so could benefit from a supplement. It is also found in a small number of foods including oily fish, red meat, liver, eggs.

VITAMIN E

WHAT: A fat-soluble direct antioxidant with anti-inflammatory properties that’s found in a wide range of seeds, nuts, vegetables, healthy oils and oily fish. WHY: Vital for a healthy immune system, smooth muscle growth and neurological functions. Like vitamin A, it can act directly to neutralise cancer-causing free radicals, which makes it a powerful ally for your immune system. However, while it’s important to correct deficiencies, in reality severe vitamin E deficiency is rare. The large Select study (Selenium and Vitamin E Cancer Prevention Trial) which gave vitamin E to a group of men over several years actually showed an increased incidence of prostate cancer. But you’re not likely to consume excessive levels of vitamin E from your diet alone — and I would encourage you to ensure your diet is rich in this vitamin. FOUND IN: Pistachios, almonds, hazelnuts, spinach, Swiss chard, fresh fruit, cruciferous vegetables, whole wheat, sunflower and pumpkin seeds, extra-virgin olive oil, sunflower oil, rapeseed oil, avocado, butternut squash, sweet potato, trout, mackerel, peas, soy and broad beans.

VITAMIN K

WHAT: Vitamin K is a collective term for a number of essential fat-soluble nutrients, the most

prominent subtypes being vitamins K1 and K2.

WHY: All K vitamins play a significant role in regulating blood flow, helping to form clots following a cut or surgery and prevent them when they are not needed. Vitamin K2 is essential for bone formation and health, ensuring that calcium is absorbed easily into the bone mass.

Fascinatingly, it has the opposite effect in the walls of your arteries — where it prevents the build-up of calcium that can harden them, leading to heart attacks, strokes and poor blood supply in the legs.

Vitamin K2 is found in fermented products — including blue-veined cheeses such as Stilton or Roquefort, so eating these can help to strengthen your good gut bacteria (which in turn helps your body to fight cancer) as well as building healthy bones.

Laboratory tests have consistently demonstrated direct anti-cancer effects of vitamin K. FOUND IN: Spinach, kale, beetroot, cabbage, green beans, chicken legs and wings, eggs, berries, avocados, grapes, pomegranates, bread, cereals, olive and sesame oils (K1). Fermented soy, fermented hard cheeses, Stilton, Gouda, Edam, egg yolk, soy beans, sauerkraut, tempura, kombucha, kimchi, natural live yoghurts and meat from grass-fed animals.